EDP Sciences
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Volume 375, Number 2, August IV 2001
Page(s) 591 - 613
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20010364

A&A 375, 591-613 (2001)
DOI: 10.1051/0004-6361:20010364

The SUMER spectral atlas of solar-disk features

W. Curdt1, P. Brekke2, 3, U. Feldman4, K. Wilhelm1, B. N. Dwivedi1, 5, U. Schühle1 and P. Lemaire6

1  Max-Planck-Institut für Aeronomie, 37191 Katlenburg-Lindau, Germany
2  Institute of Theoretical Astrophysics, University of Oslo, Blindern, 0315 Oslo 3, Norway
3  ESA Space Science Department / NASA Goddard Space Flight Center, Greenbelt, Md. 20771, USA
4  E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington D.C., 20375, USA
5  Department of Applied Physics, Banaras Hindu University, Varanasi 221005, India
6  Institut d'Astrophysique Spatiale, Unité Mixte CNRS -Université de Paris XI, 91405 Orsay Cedex, France

(Received 15 December 2000 / Accepted 7 March 2001 )

A far-ultraviolet and extreme-ultraviolet (FUV, EUV) spectral atlas of the Sun between 670 Å and 1609 Å in the first order of diffraction has been derived from observations obtained with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft SOHO (Solar and Heliospheric Observatory). The atlas contains spectra of the average quiet Sun, a coronal hole and a sunspot on the disk. Different physical parameters prevalent in the bright network (BN) and in the cell interior (CI) -contributing in a distinct manner to the average quiet-Sun emission -have their imprint on the BN/CI ratio, which is also shown for almost the entire spectral range. With a few exceptions, all major lines are given with their identifications and wavelengths. Lines that appear in second order are superimposed on the first order spectra. These lines are clearly marked in the atlas. The spectra include emissions from atoms and ions in the temperature range $6\times10^3$ K to $2\times10^6$ K, i.e., continua and emission lines emitted from the lower chromosphere to the corona. This spectral atlas, with its broad wavelength coverage, provides a rich source of new diagnostic tools to study the physical parameters in the chromosphere, the transition region and the corona. In particular, the wavelength range below 1100 Å as observed by SUMER represents a significant improvement over the spectra produced in the past. In view of the manifold appearance and temporal variation of the solar atmosphere, it is obvious that our atlas can only be a - hopefully typical -snapshot. Brief descriptions of the data reduction and calibration procedures are given. The spectral radiances are determined with a relative uncertainty of 0.15 to 0.30 ($1\sigma$) and the wavelength scale is accurate to typically 10 mÅ. The atlas is also available in a machine readable form.

Key words: Sun: UV radiation -- Sun: chromosphere -- Sun: transition region -- Sun: corona -- line: identification -- atlases

Offprint request: W. Curdt, curdt@linmpi.mpg.de

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